President-in-Waiting Faces Angry, Mobilized Workforce

CAIRO—One group among Egypt's 87 million people threatens to disrupt the widespread public adulation expected to propel Abdel Fattah Al Sisi into the presidential palace: workers.

Trade union activists and workers played a key role in unseating former President Hosni Mubarak and his successor, Mohammed Morsi. Now their increasingly aggressive tactics in pursuit of wage increases pose a formidable political challenge to Mr. Sisi, who...